Identifies qualifier annotations. Anyone can define a new qualifier. A qualifier annotation:

• is annotated with @Qualifier, @Retention(RUNTIME), and typically @Documented.
• can have attributes.
• may be part of the public API, much like the dependency type, but unlike implementation types which needn't be part of the public API.
• may have restricted usage if annotated with @Target. While this specification covers applying qualifiers to fields and parameters only, some injector configurations might use qualifier annotations in other places (on methods or classes for example).

For example:

  @java.lang.annotation.Documented
  @java.lang.annotation.Retention(RUNTIME)
  @javax.inject.Qualifier
  public @interface Leather {
    Color color() default Color.TAN;
    public enum Color { RED, BLACK, TAN }
  }